Just before sunset on Monday in Athens, Michael Phelps climbed atop his starting block to swim the final of the 200-meter freestyle. The stadium flags were stretched horizontal in a brisk wind on this third day of the most ambitious Olympics attempted by any swimmer in history. Yet this race was more than just a part of the Phelps package. It was the quest within the quest, an island of personal challenge. Hall of Fame coach Paul Bergen called it "the race of the century," and when that drew chuckles from listeners suspicious of hyperbole, he added, "Really."

In lane 3 was Phelps, 19, the face of these Games. In lane 5 was Ian Thorpe, the Australian national treasure who had been similarly positioned in Sydney four years ago and now, at 21, remained near the top of his form and very much at the peak of eminence in the sport. Between them was defending Olympic champion Pieter Van den Hoogenband, the Dutchman who shocked Thorpe in the Sydney 200 free. Further outside were Grant Hackett, another gifted Aussie, and Klete Keller, another gifted Yank. This was not just the Olympic Games, it was the Fantasy Final of swim races.

Phelps had hurtled toward Athens since making the U.S. Olympic team as a 15-year-old in 2000. In the interim he had broken world records 11 times, won five world championships, established himself as the most versatile swimmer in history and entered eight Olympic events after signing an endorsement deal with Speedo that would pay him $1 million if he could match Mark Spitz's iconic seven gold medals from 1972. As the Games approached, Phelps chafed at the waiting. "I wish the meet started six months ago," he told SI from his room in the Olympic Village on the night of the opening ceremonies. "I feel awesome in the water in training. I need to get in the pool and swim fast soooo bad."

He began his mission right on cue with a gold medal--breaking his own world record--in the 400-meter individual medley last Saturday night, and then he added a bronze Sunday night in the 4X100-meter freestyle relay. The 200 free, though, was a unique contest. It was not Phelps's strongest event, yet this was where he could stretch himself to the furthest edges of his talent and swim against Thorpe and Van den Hoogenband on their turf. In the weeks leading to the Olympics, Spitz had questioned why Phelps, in pursuit of gold medals and green money, would swim an event in which victory was unlikely. The answer was simple. "I wanted to race Thorpe in a freestyle before we were both done," said Phelps. (Last summer at the world championships in Barcelona, Phelps beat Thorpe in both the 200- and 400-meter individual medleys, Phelps's strongest races.)

"If this was just about seven gold medals," said Phelps's coach, Bob Bowman, just before the Games opened, "he would have dropped this event. But that's not the goal. The goal is to see what he can do."

Thorpe had played a role in Phelps's development more than two years earlier. Thorpe had broken the world record in the 400 free in 1998, when he was 15 years old, and Bowman had made a tape of that race and played it endlessly for his own adolescent pupil, beseeching him to absorb the smooth power in Thorpe's stroke. "I used that tape as the model for Michael's freestyle stroke," says Bowman. "We spent an awful lot of time watching."

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Phelps watched more than just Thorpe's stroke. "I remember the first time I saw him on camera, on TV," says Phelps. "He was really good and so poised. The way he presented himself was incredible. I knew I wanted to handle myself just like that."

Each calls the other a friend, but there have been hiccups in the relationship. In spring 2003 Thorpe informally invited Phelps to train with him after learning that Phelps had scheduled a trip to Australia in late fall of that year. However, when Phelps arrived, Thorpe was elsewhere. "I was disappointed," said Phelps in Athens, "but I'm over it now." In December, Thorpe said it was "unattainable" for anyone to win seven gold medals. Phelps responded that perhaps Thorpe meant it was impossible for him.

On this night Thorpe reaffirmed his greatness, adding the 200-meter gold medal to the 400-meter gold he took on the first night of the Games. His winning time of 1:44.71 equaled his own third-fastest time in history, as he overhauled Van den Hoogenband in the final 50 meters. Phelps nearly caught the Dutchman as well and took the bronze in 1:45.32, breaking his year-old American record. Phelps came away with an even deeper respect for Thorpe--"It's unbelievable how he moves through the water," Phelps said--but also feeling fulfilled at having pushed himself and unfazed by the fact that the million-dollar bonus for seven golds had gone down the drain. "I was happy to be part of this field and to do my best time," he said. "It was fun."

And his quest would continue. He was the heavy favorite in last Tuesday night's 200-meter butterfly (after SI's press deadline) and later that same night would anchor the U.S.'s 4X200-meter freestyle relay team, which was almost certain to win a medal, with a chance at gold. Three more races remained, as did his chance of becoming the second athlete in history to win eight medals in one Games. Said U.S. teammate Aaron Peirsol, who won a gold medal Monday night in the 100-meter backstroke, "That's the Spitzian accomplishment in our age."

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Upon his arrival in Athens, the preternaturally calm Phelps spent most of his time in his room in the Olympic Village watching movies from his collection of more than 40 DVDs on his PS2 console and playing Madden 2004 with his roommate, graybeard triple-gold-medalist Lenny Krayzelburg. With his first race scheduled early last Saturday morning, Phelps didn't march in Friday night's opening ceremonies, but he mingled in the Village with athletes who were preparing to participate. "I was just talking with [softball pitcher] Jennie Finch,'' Phelps said by phone on the night of the ceremonies. "I saw Andy Roddick. The basketball team was there: Iverson, LeBron, Carmelo. Awesome. That gets you ready.'' He went back to his room and fell asleep before 10 p.m. and less than 24 hours later walked onto the deck of the Olympic pool, headphones strapped over his racing cap, Eminem's "Till I Collapse" filling his ears: When you feel weak, you feel like you wanna just give up/But you gotta search within you, you gotta find that inner strength/And just pull that s--- out of you....

It was there that his coolness cracked. He had never felt quite so nervous as he did in the moments before the start of the 400 IM. He swam raggedly, still broke his world record and won by more than three seconds over teammate Erik Vendt, who took the silver, as he had in Sydney.

An hour after the race Phelps's mother, Debbie, caught up with her son. She had raised him as a single mother after getting a divorce when Michael was seven, and mother and son are as close as brother and sister. She, her two daughters and several other relatives were waiting against a fence outside the pool area. When Michael saw her, he walked to the fence, raised his medal and said--as innocently as a child--"Mom, look.'' Then they all cried together for a moment.

The second medal would be less satisfying. In the 4X100 free relay Ian Crocker, who had been complaining of a sore throat for three days, was nonetheless allowed to swim the leadoff leg by U.S. men's coach Eddie Reese, who also coached Crocker at Texas. Crocker swam a horrific 50.05-second split, leaving the U.S. in last place. Phelps, then Neil Walker, moved the U.S. into third, but they had to settle for the bronze behind South Africa and the Netherlands, the poorest 4X100 finish in Olympic history for the U.S.

There was little time for Phelps to suffer. Forty-one minutes after chasing home Thorpe and Van den Hoogenband, he was called to swim the semifinals of the 200 fly. Phelps knifed into the pool, briefly parting the warm water behind him, chasing more medals that lay in front.